Five children have been injured in a school in eastern China after a man attacked them with an iron hammer before burning himself to death.

Wang Yonglai, a farmer, broke down a side gate of the Shangzhuang primary school in Weifang City with his motorcycle before the attack, the state-run Xinhua news agency said.

Friday's attack in Shandong province is the latest in a string of assaults on children at schools across the country.

Wang struck out at the children and a teacher before pouring petrol over his body, grabbing two children and setting himself on fire.

Teachers managed to pull the children away but the man died at the scene.

Doctors said the children's injuries were not life-threatening, according to Xinhua.

Security strengthened

The ministry of education on Friday issued an "urgent" notice calling on schools to strengthen security, tighten restrictions on campus visitors and devise emergency plans.

"We must establish a safety first, prevention first concept," the ministry said in the notice, posted on its website.

Authorities across China have already ordered stepped-up security at schools and tighter monitoring of people known to be mentally ill.

Police show teachers how to stop attackers as part of increased security measures [AFP]

Police in a western district of Beijing have distributed 200 pitchfork-like implements to schools, for use by campus security and teachers to keep any attackers at bay, the Beijing News reported.

On Thursday, 29 children were hurt, five critically, when a man attacked them with a knife in Jiangsu province.

Two teachers and a security guard were also injured by the 47-year-old attacker who has since been detained.

Police said the man carried out the attack out of anger over a "series of business and personal humiliations", according to Xinhua.

On Wednesday, a teacher who had been on sick leave since 2006 for mental problems injured at least 15 students and a teacher in a knife attack at a primary school in Guangdong province, in southern China.

In that attack, Chen Kanbing, 33, jumped from the school building after stabbing the children, in an apparent suicide attempt, before being arrested by police.

Also on Wednesday, the authorities in Fujian province in the southeast executed Zheng Minsheng, a doctor, for stabbing to death eight children outside their elementary school on March 23.

Police said Zheng, 41, used a dagger to stab children in the neck, chest, stomach and back in a fit of rage and depression after splitting from his girlfriend.

Zheng had admitted "intentionally killing" the children at a trial earlier this month and unsuccessfully appealed against the death penalty.